The Owyhee River is a tributary of the Snake River located in northern Nevada, southwestern Idaho and southeastern Oregon in the United States. It is 280 miles (450 km) long. The river's drainage basin is 11,049 square miles (28,620 km2) in area, one of the largest subbasins of the Columbia Basin. The mean annual discharge is 995 cubic feet per second (28.2 m3/s), with a maximum of 50,000 cu ft/s (1,400 m3/s) recorded in 1993 and a minimum of 42 cu ft/s (1.2 m3/s) in 1954.

The Snake River is a major river in the interior Pacific Northwest region of the United States. About 1,080 miles (1,740 km) long, it is the largest tributary of the Columbia River, which is the largest North American river that empties into the Pacific Ocean. Beginning in Yellowstone National Park, western Wyoming, it flows across the arid Snake River Plain of southern Idaho, the rugged Hells Canyon on the borders of Idaho, Oregon and Washington, and finally the rolling Palouse Hills of southeast Washington. It joins the Columbia River just downstream from the Tri-Cities, Washington, in the southern Columbia Basin.